Pressure switch having head portions held by groove means



Sept. 27, 1966 .J. WEAVER 3,275,769

PRESSURE 3 CH ING HEAD PORTIONS HELD OVE MEANS File e0. 1965 INVENTOR. PAUL J. WEA VER A TTORNEYS.

United States Patent "ice 3,275,769 PRESSURE SWITCH HAVlNG HEAD PORTIONS HELD BY GROOVE MEANS Paul J. Weaver, Pasadena, Calif., assignor to Armand C. Anderson, Alhambra, Calif. Filed Dec. 17, 1963, Ser. No. 331,176 4 Claims. (Cl. 200-82) This invention relates to a pressure switch.

Pressure switches have the function of changing their switching condition when exposed to a predetermined fluid pressure. There are many such switches to be found on the market, all of which perform the same function. They are made in varying degrees of complexity and to varying degrees of accuracy and adjustability. The objects of this invention are to provide a pressure switch with the features of facile and wide-range adjustability, easy manufacture from simple components, and ruggedness of construction.

A pressure switch according to this invention includes a switch having a contact that is movable to change the switching condition of the switch. The device also has an actuator for said contact comprising a body having .a passage opening through the body at a first and second end of the passage. One end of the body is adapted to provide means for actuating the switch. A second end of the passage is adapted for connection to a source of fluid pressure to which the actuator is responsive. An axial bore in the body at the second end receives a piston which makes a sliding and fluid-sealing fit with the wall thereof. One end of this piston is exposed to fluid pressure, and the piston is so disposed and arranged as to move the contact when exposed to a predetermined pressure. Spring means is interposed between the body and the piston in opposition to the fluid pressure, and means is provided for adjusting the initial loading of the spring.

According to a preferred but optional feature of the invention, the spring means is disposed between the first end of the passage and a button, which button is adapted to be abutted by the piston and carried by it in response to motion of the piston.

According to still another preferred but optional feature of the invention, a screw is provided in the body for adjusting the position at the first end against which the spring abuts.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings in which:

FIG. 1 is a side elevation partly in cutaway cross-section showing the presently preferred embodiment of the invention; and

FIG. 2 is a cross-section taken at line 22 of FIG. 1.

FIG. 1 illustrates a pressure switch according to the invention wherein a micro-switch 11 is provided to change the switching conditions at its terminals 12, 13. A typical switching arrangement would be normally closed in the condition illustrated, and adapted to be opened when contact 14 is moved.

A spacer 15 accurately locates the micro-switch relative to a mounting bracket 16. This bracket is mounted to a body 17, which body includes a tube 18 having first and second ends 19, 20.

As can best be seen in FIG. 2, the tube is undercut with grooves 21, 22 at both its ends, and first and second heads 23, 24 are placed inside the tube. Then segments 25, 26, 27 are inserted in the respective grooves so as to be contacted by a limiting shoulder 28 on the respective head. Each of the segments is less than 120 in are, so that they can readily be inserted into the respective groove when the head is moved far enough into the tube that the limiting shoulder does not overhang the segments.

3,275,769 Patented Sept. 27, 1966 Then, when the segmentsare in place, they may lightly be cemented in place, if desired as an assistance in assembly, and then the head will be moved toward its respective end with the limiting shoulder holding the segments in the groove. This arrangement prevents expulsion or removal of the heads from the tube without first removing the segments. The head construction is generally the same at both ends, as is that of the segments. Therefore, only the construction at the first end has been described and illustrated in detail.

Bracket 16 has a hole 29 therethrough, through which threaded end 30 of head 23 passes. The bracket bears against the tube. A nut 31 is threaded onto the threaded end 30, and both draws the head against the segment and tightens the bracket onto the tube so that all is firmly mounted.

Head 23 has an internally-threaded first bore 32 which receives a screw 33. This screw can be threaded to the right and left in FIG. 1 by turning it in first bore 32. The screw has a smooth-bored passage 34 therethrough which lies on central axis 35 of the device, this central axis intersecting contact 14.

Passage 34 acts as a guide for a piston extension 36, this extension comprising a simple pin having a shoulder 37 formed thereon. A first button 38 surrounds the piston extension and makes a loose fit therewith. It has a central opening 39 ending at a chamfer 40, which chamfer is smaller in diameter than a matching surface on the inner end of screw 33 so that button 39 will strike and be backed up by the screw. Button 38 has a backing shoulder 41 for a force spring 42. This force spring presses against a second butt-on 43 which is generally similar to the first button. A bias spring 44 is opposed between the button and shoulder 37 on the piston extension which biases the piston extension toward the right in FIG. 1.

A bore 45 is formed in second head 24 which slidingly receives piston 46. The left-hand end of piston 46 is adapted to abut and bear against the right-hand end of the piston extension so that the piston extension and the piston can in operation be considered a piston in their entirety. Chamfer 47 on second button 43 has a smaller diameter than a matching chamfer 48 on the left-hand end of piston 46 so that they strike each other when the piston is moved far enough to the left. An O-ring 49 seals between piston 46 and nut 50, which nut is threaded onto second head 24. The ring renders the sliding fit between bore 45 and piston 46 a fluid-sealed fit.

A snap ring 51 is seated in a groove 52 near the righthand end of the piston. An adapter 53 is threaded onto nut 50, leaving a space between the two where the snap ring may move in an axial direction, the snap ring serving to limit the total axial movement of the piston, thereby serving to protect the switch from over-travel by its engagement with face 54 of nut 50.

A washer 55 and nut 56 are provided for mounting the device to any desired structure. Opening 57 forms part of a passage through the body and is adapted by means of the washer and nut to be attached to other structure. Internal threads 58 provide means for connection to nipples or other sources of fluid pressure (not shown) which pressure actuates the device.

In the terminology used herein, the entire assembly shown in FIG. 1 is described as a pressure switch. The portion held by the bracket is the switch itself, while the portion to the right of the bracket may for convenience be described as an actuator. The term body is used herein to mean the assembly of tube and heads.

The operation of the device should be evident from the foregoing. The bias spring tends to keep the piston extension biased against the piston, and the piston biased to the right in FIG. 1. The initial loading of the device is accomplished by adjustably compressing force spring 42. This is accomplished by turning screw 33 so as to adjust this compression, the first button bearing against the screw, and the second button bearing against the second head. When pressure is exerted at opening '57, the piston will be moved to the left, striking the second button and carrying it and the piston extension to the left. The amount of force needed to be overcome in order for the piston to move the distance necessary for the piston extension to strike contact 14 and change the switching condition of switch 11 is the total of the initial spring load plus the load determined by the spring constant and the distance which it must travel.

In the event of over-pressures at opening 57, the device is protected, because the snap ring will simply abut against face 54, and the forces will not be felt by any part of the system.

It will thereby be seen that this device is of simple construction, delicate in wide-range adjustability, and made of readily-obtainable and easily-duplicated parts.

This invention is not to be limited by the embodiment shown in the drawings and described in the description which is given by way of example and not of limitation, but only in accordance with the scope of the appended claims.

I claim:

1. A pressure switch adapted to change its switching condition in response to a predetermined fluid pressure, comprising: a switch comprising a contact movable to change the switching condition of the switch; and an actuator connected to the switch comprising a body tube having an axis and a first end an a second end, a first and a second head in the respective ends of the body tube, a first and a second axial bore passing through the respective first and second heads, the first bore being adjacent to the switch, and the second head being adapted to connect the second bore to a source of pressure to which the actuator is responsive, a first and a second piston, said second piston slidably fitted in the second bore, the second piston making a fluid sealing fit in the second bore, one end of the second piston being exposed to said fluid pressure at the second end, force spring means interposed between the body and the second piston in opposition to said fluid pressure; means for adjusting the initial loading of the force spring means comprising a tubular screw threaded into said first bore, said first piston slidably fitted in said tubular screw, the force spring means being backed up by the tubular screw, a protrusion on said second piston, a pair of axially spaced apart surfaces on said actuator adapted to be engaged by the protrusion to limit the axial movement of the second piston, a pair of axially spaced apart internal undercut grooves in the body tube, a shoulder on each head, and a segment in each of said grooves which segment projects into the body tube to radially overlap the respective shoulder and thereby prevent expulsion of the heads from the tube.

2. An actuator for a switch, said actuator adapted to change the condition of the switch in response to a predetermined fluid pressure comprising: a body tube having an axis and a first end and a second end, a first and a second head in the respective ends of the body tube, a first and a second axial bore passing through the respective first and second heads, the first bore being adapted to face the switch, and the second head being adapted to connect the second bore to a source of pressure to which the actuator is responsive, a first and a second piston, said second piston slidably fitted in the second bore, the second piston making a fluid sealing fit in the second bore, one end of the second piston being exposed to said fluid pressure at the second end, force spring means interposed between the body and the second piston in opposition to said fluid pressure; means for adjusting the initial loading of the force spring means comprising a tubular screw threaded into said first bore, said first piston slidably fitted in said tubular screw, the force spring means being backed up by the tubular screw, a protrusion on said second piston, a pair of axially spaced apart surfaces on said actuator adapted to be engaged by the protrusion to limit the axial movement of the second piston, a pair of axially spaced apart internal undercut grooves in the body tube, a shoulder on each head, and a segment in each of said grooves which segment projects into the body tube to radially overlap the respective shoulder and thereby prevent expulsion of the heads from the tube.

3. A pressure switch according to claim 1 in which a first and second button are provided within the tube surrounding said first and second pistons respectively, and abutting the tubular screw and the second piston, respectively, the force spring being in abutting contact with the two buttons.

4. An acuator according to claim 2 in which a first and second button are provided within the tube surrounding said first and second pistons respectively, and abutting the tubular screw and the second piston, respectively, the force spring being in abutting contact with the two buttons.

References Cited by the Examiner UNITED STATES PATENTS 11/1923 Hartman ZOO-82 3/1933 Dennis 200-82 

1. A PRESSURE SWITCH ADAPTED TO CHANGE ITS SWITCHING CONDITION IN RESPONSE TO A PREDETERMINED FLUID PRESSURE, COMPRISING: A SWITCH COMPRISING A CONTACT MOVABLE TO CHANGE THE SWITCHING CONDITION OF THE SWITCH; AND AN ACTUATOR CONNECTED TO THE SWITCH COMPRISING A BODY TUBE HAVING AN AXIS AND A FIRST END AND A SECOND END, A FIRST AND A SECOND HEAD IN THE RESPECTIVE ENDS OF THE BODY TUBE, A FIRST AND A SECOND AXIAL BORE PASSING THROUGH THE RESPECTIVE FIRST AND SECOND HEADS, THE FIRST BORE BEING ADJACENT TO THE SWITCH, AND THE SECOND HEAD BEING ADAPTED TO CONNECT THE SECOND BORE TO A SOURCE OF PRESSURE TO WHICH THE ACTUATOR IS RESPONSIVE, A FIRST AND A SECOND PISTON, SAID SECOND PISTON SLIDABLY FITTED IN THE SECOND BORE, THE SECOND PISTON MAKING A FLUID SEALING FIT IN THE SECOND BORE, ONE END OF THE SECOND PISTON BEING EXPOSED TO SAID FLUID PRESSURE AT THE SECOND END, FORCE SPRING MEANS INTERPOSED BETWEEN THE BODY AND THE SECOND PISTON IN OPPOSITION TO SAID FLUID PRESSURE; MEANS FOR ADJUSTING THE INITIAL LOADING OF THE FORCE SPRING MEANS COMPRISING A TUBULAR SCREW THREADED INTO SAID FIRST BORE, SAID FIRST PISTON SLIDABLY FITTED IN SAID TUBULAR SCREW, THE FORCE SPRING MEANS BEING BACKED UP BY THE TUBULAR SCREW, A PROTRUSION ON SAID SECOND PISTON, A PAIR OF AXIALLY SPACED APART SURFACES ON SAID ACTUATOR ADAPTED TO BE ENGAGED BY THE PROTRUSION TO LIMIT THE AXIAL MOVEMENT OF THE SECOND PISTON, A PAIR OF AXIALLY SPACED APART INTERNAL UNDERCUT GROOVES IN THE BODY TUBE, A SHOULDER ON EACH HEAD, AND A SEGMENT IN EACH OF SAID GROOVES WHICH SEGMENT PROJECTS INTO THE BODY TUBE TO RADIALLY OVERLAP THE RESPECTIVE SHOULDER AND THEREBY PREVENT EXPULSION OF THE HEADS FROM THE TUBE. 